1. Technical Field
The present invention relates to horology and, in particular, to methods and devices for time measurement using an electrical time base. Still more particularly, the present invention provides a method and system for expiring a device after a predetermined amount of time has elapsed.
2. Description of Related Art
Portable electronic devices have become ubiquitous, and as the size and cost of electronic circuits continues to be reduced, electronic devices continue to be incorporated in an increasing number of consumer products. As an example, paper greeting cards that play music when opened are no longer considered a novelty. Technical progress has been made on flexible circuits that will allow electronic circuits to created in a variety of shapes and to be embedded into more products.
Inexpensive electronic devices can be categorized based upon their power requirements or associated power systems. Some electronic devices have a variety of functions that may require the device to be powered by an external power source, such as an electrical outlet via an AC-DC adapter, while some devices require one or more batteries. Other devices may require both types of power sources: an external power source for enabling most functions, and a small battery for powering minor functions, such as a clock or timekeeping function, while not connected to an external power source or while “turned off”. Small electronic devices frequently incorporate a small, flat battery, similar to those that power electronic watches, merely to power a clock circuit. Generally, the battery powers some type of time base oscillator or pulse generator that measures the passage of units of time. Devices may also contain a tiny, simple, electronic, horological device or “time cell” that provides time measurement without a battery, radioactivity, or an oscillator as described in incorporated U.S. patent application Ser. Nos. 09/703,340 and 09/703,334.
There are many credit card-like “value cards” for telephone service, grocery store discounts, frequent flyer miles, hotel door entry, and purchases. Smart cards are prime examples of value cards that may be made to contain a time cell. Some value cards have expiration dates. Enforcement of the expiration date can be difficult. For example, if a credit card has an expired date, a person must identify that the credit card is expired by receiving a rejection from a central server for the credit card and/or verifying that the current date is greater than the expired date. Current expiration methods include manual processes, such as cutting a credit card in half, expiring a value card using an external card reader with a reasonably correct time setting, and expiring a value card at a central server.
Therefore, it would be advantageous for a device to self-destruct after a predetermined amount of time has elapsed.